1. Technical Field
The present invention relates to an ozone processing device which discharges a processing gas containing at least ozone onto the surface of a substrate such as a semiconductor substrate or a liquid crystal substrate in order to form or to improve an oxide film on the substrate surface or to remove a resist film formed on the substrate surface.
2. Description of the Related Art
FIG. 7 and FIG. 8 show examples of conventional ozone processing devices. FIG. 7 is a cross-section drawing showing a portion of an ozone processing device based on a conventional technology and is a cross-section drawing along the E-E line in FIG. 8. FIG. 8 is a bottom-view drawing along the D-D line in FIG. 7.
As FIG. 7 and FIG. 8 show, an ozone processing device 100 is equipped with: a mounting base 101 on which a substrate K is mounted; a gas supply head 102 disposed above the mounting base 101 so that it faces the substrate K. The mounting base 101 and the gas supply head 102 are disposed in a chamber (not illustrated) equipped with a closed space. The chamber (not illustrated) is formed with a suitable exhaust opening from which internal gasses are discharged to the outside.
The mounting base 101 is equipped with an internal heating device (not illustrated) formed from a heater. The substrate K mounted on the upper surface is heated by this heating device (not illustrated). Also, the mounting base 101 can be raised and lowered by a raising/lowering device (not illustrated).
The gas supply head 102 is formed from a nozzle module 103 and a cooling module 104, both formed as block-shaped members that are stacked vertically and bonded. A cavity 105 is formed on the upper surface of the nozzle module 103, i.e., the surface where it bonds with the cooling module 104. Nozzles 106, which communicate with the cavity 105 and open on the lower surface, are arranged in a plurality of rows in a staggered manner. Exhaust grooves 107, which open on the side surfaces, are formed on the bottom surface between the rows of the nozzle 106.
The cooling module 104 is formed from an upper member 104a and a lower member 104b, which are stacked vertically and bonded. A cooling fluid path 108 (108a, 108b) is formed on the bonding surface between the upper member 104a and the lower member 104b in a zigzag pattern extending from one side surface to the other side surface. The cooling fluid path 108 is connected by way of pipes 109, 110 to external cooling fluid supplying means 111. In this manner, the cooling fluid path 108, the pipes 109, 110, and cooling fluid supplying means 111 form a circulation path for cooling fluid to allow the cooling fluid to circulate.
The cooling module 104 is formed with a through-hole 112 that passes from the upper surface to the lower surface and communicates with the cavity 105. This through-hole 112 is connected by way of a pipe 114 connected thereto to an external ozone gas generating device 113. A predetermined concentration of ozone gas (processing gas) is supplied from ozone gas generating means 113 by way of the pipe 114 and the through-hole 112 to the cavity 105, and is discharged toward the substrate K from the lower openings of the nozzle 106.
With the ozone processing device 100 described above, the substrate K is mounted on the mounting base 101. The substrate K is mounted on heating means (not shown) and the mounting base 101 is raised by raising/lowering means (not shown) to a position, as shown in FIG. 7, where it is separated by a predetermined space from the gas supply head 102.
Then, the ozone gas is supplied from ozone gas generating device 113 to the cavity 105 by way of the pipe 114 and the through-hole 112, and this is blown toward the substrate K from the lower openings of the nozzles 106.
The ozone gas flows discharged from the nozzles 106 in this manner run into the surface of the substrate K, flow along the surface, and run into each other to form a flow toward the exhaust grooves 107. During this flow, the ozone (O3) is heated by the substrate K. This heating and the contact with the substrate K and the resist cause the gas to break down into oxygen (O2) and active oxygen (O*). This active oxygen (O*) forms an oxide film on the surface of the substrate K, improves the oxide film on the surface of the substrate K, or removes the resist film formed on the surface of the substrate K by a thermochemical reaction with the active oxygen (O*).
Then, the ozone gas that flows into the exhaust grooves 107 after the processing it performs is exhausted by way of the exhaust grooves 107 from between the substrate K and the gas supply head 102.
In this ozone processing device 100, the gas supply head 102 is cooled by a cooling fluid, and the ozone gas that flows through the through-hole 112, the cavity 105, and the nozzle 106 is cooled by the cooling fluid. Thus, the ozone gas flowing through the through-hole 112, the cavity 105, and the nozzle 106 is prevented from undergoing thermal decomposition due to increased temperature, thus preventing the ozone concentration from dropping due to thermal decomposition.
Also, since the substrate K and the gas supply head 102 are brought close to each other so that the lower openings of the nozzles 106 can be near the substrate K, the ozone discharged from the nozzles 106 is prevented from being thermally decomposed before it reaches the substrate K and a thinner layer of ozone gas flowing on the substrate K is provided. This allows more ozone to contribute to the formation of the oxide film, the improvement of the oxide film, or the removal of the resist film.
In this conventional ozone processing device 100, the gas supply head 102 is positioned close to the substrate K as described above. This causes heat to transfer from the substrate K and the mounting base 101 to the gas supply head 102, resulting in an increase in temperature in the gas supply head 102.
Because the volume (capacity) of the gas supply head 102 is high and is cooled with the cooling fluid described above, thermal equilibrium in the substrate K and the gas supply head 102 becomes difficult to achieve and takes a long time. As a result, the temperature of the substrate K does not stay constant over a long period of time, leading to unevenness in the ozone processing operation.
Also, the processing gas discharged from the nozzles 106 flow into the exhaust grooves 107. The processing gas discharged from the nozzles 106 toward the center of the nozzle module 103 is discharged from the nozzles 106 disposed toward the ends because the gas discharged from the nozzles 106 flow into the exhaust grooves 107. The gas flowing into the exhaust grooves 107 obstructs the flow within the exhaust grooves 107, making it difficult for the gas discharged from the nozzles 106 toward the center from being exhausted out between the substrate K and the gas supply head 102.